1const arr = [1, 2, 3, 4];
2const sum = arr.reduce((a, b) => a + b, 0);
3// sum = 10

1function getArraySum(a){
2    var total=0;
3    for(var i in a) { 
4        total += a[i];
5    }
6    return total;
7}
8
9var payChecks = [123,155,134, 205, 105]; 
10var weeklyPay= getArraySum(payChecks); //sums up to 722

1[1, 2, 3, 4].reduce((a, b) => a + b, 0)

1const addSum = function (arr) {
2  return arr.reduce((acc, cur) => (acc += cur), 0);
3};